Sarah Brown
Mushrooms are a nutritious food with many health benefits. However, they contain varying levels of oxalates, which can cause health issues for some people. The oxalate content of mushrooms depends on the type of mushroom and its preparation. For example, Chaga mushrooms have been linked to oxalate nephropathy, a condition caused by the buildup of oxalate crystals in the kidneys. Other mushrooms, like white button and shiitake mushrooms, contain mostly insoluble oxalates, which are not easily absorbed into the bloodstream. Oyster mushrooms are moderately high in oxalates, but their soluble oxalate content can be reduced by cooking. Overall, while mushrooms can be a healthy part of a balanced diet, it is important to be aware of their oxalate content, especially for individuals with kidney issues or those at high risk for kidney stones.
| Characteristics | Values |
|---|---|
| Mushrooms with high oxalate content | Chaga, White button, Shiitake, Oyster, Morels, Chanterelles |
| Mushrooms with moderate oxalate content | Lion’s Mane, Cauliflower, Reishi, Button, Straw, Oyster, Enokitake |
| Mushrooms with low oxalate content | Lion’s Mane, Cauliflower, Reishi |
| Oxalate content of raw, commercially grown mushrooms | 58.9 to 104.1 mg/100 g DM |
| Oxalate content of cooked mushrooms | 48.9 to 124.6 mg/100 g DM |
| Oxalate content of mushrooms harvested from forests | 29.3 to 40.2 mg/100 g DM |
| Forms of oxalate | Soluble, Insoluble |
| Impact of cooking on oxalate content | Marginally lowers soluble oxalate content |
| Impact of preparation on oxalate content | Water-prepared mushrooms have lower oxalate levels than dried or powdered mushrooms |
| Health risks associated with high oxalate intake | Kidney stones, Acute oxalate nephropathy, End-stage renal disease |
| Recommended daily oxalate intake for stone prevention | Below 100 mg, ideally around 50 mg |
| Mean daily intake of oxalate in English diets | 70-150 mg |
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What You'll Learn
Chaga mushrooms and kidney health
Chaga mushrooms are a type of fungus belonging to the Hymenochaetaceae family. They are parasitic on birch and other tree species. Chaga mushrooms are rich in vitamins, minerals, and nutrients. They are widely used in folk remedies and alternative medicine. However, they also contain oxalates, which can pose a risk to kidney health.
Oxalates are naturally occurring substances in food that can be either soluble or insoluble. Insoluble oxalates are bound to minerals such as calcium and magnesium, making them harder to absorb. They pass through the digestive system without being absorbed and are generally not a cause for concern. On the other hand, soluble oxalates release negatively charged ions called anions, which can enter the bloodstream. These anions can bind with calcium to form calcium oxalate crystals, which can increase the risk of gout, kidney stones, and physical damage to the kidneys.
Chaga mushrooms have been found to contain both soluble and insoluble oxalates. While the insoluble oxalates in Chaga mushrooms may not pose a significant risk, the soluble oxalates can be a concern. High consumption of Chaga mushrooms, especially in concentrated forms like supplements and powders, can lead to a significant increase in oxalate levels in the body. This, in turn, can result in a build-up of oxalate crystals in the kidneys, a condition known as oxalate nephropathy or acute kidney injury (AKI).
Several case reports have linked the long-term ingestion of Chaga mushroom powder to the development of end-stage renal disease and oxalate nephropathy. In one case, a 49-year-old Korean man with no history of kidney disease developed end-stage renal disease after consuming Chaga mushroom powder for five years. Another case involved a 69-year-old man who ingested Chaga mushroom powder for three months and developed acute kidney injury with nephrotic syndrome. These cases suggest an association between Chaga mushroom consumption and kidney health issues.
It is important to note that the risk of Chaga mushroom-induced oxalate nephropathy may be underestimated. The occurrence of this condition may be higher than reported, especially with the growing popularity of Chaga mushroom-based products. Therefore, individuals with kidney health issues or a predisposition to kidney stones should exercise caution when consuming Chaga mushrooms. It is always advisable to consult a healthcare professional before introducing any new supplement or dietary change, especially for those with existing health concerns.
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Oyster mushrooms and oxalate content
Oyster mushrooms are moderately high in oxalates, with 90% of them being soluble. They contain comparable amounts of oxalates to chocolate, almonds, and grains. Soluble oxalates can be harmful to those prone to kidney stones as they can increase the body's overall oxalate load. This is because soluble oxalates release free oxalate anions, which can pass into the bloodstream and bind with free calcium to make calcium oxalate crystals.
However, it is important to note that not all oxalate-rich foods will lead to kidney stones, as the chemistry is more complex. Additionally, cooking marginally lowers the soluble oxalate content of mushrooms. The levels of soluble and insoluble oxalates in mushrooms are also generally low compared to other common oxalate-containing vegetables.
For those concerned about oxalate intake, it is recommended to consult a healthcare provider for tailored advice. It is also important to consider the preparation and type of mushroom when considering oxalate content. For example, fresh mushrooms have varying oxalate levels, with morels, shiitakes, and chanterelles having higher levels. Drying mushrooms does not change the oxalate content per gram, but it may be easier to use more dried mushrooms, leading to a higher oxalate intake. Powdered mushrooms are also more concentrated in oxalates, so it is important to watch portion sizes.
Overall, while oyster mushrooms are moderately high in oxalates, the amount they contain is comparable to other commonly consumed foods, and cooking can help to lower the oxalate content.
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Cooking methods and oxalate levels
Mushrooms are moderately high in oxalates but have good nutritional value. Chaga mushrooms, in particular, are high in oxalates and can cause oxalate nephropathy, a sudden drop in kidney function. White button and shiitake mushrooms are also very high in oxalates, but 99% of them are insoluble, so they are not a concern for causing hyperoxaluria. Oyster mushrooms are moderately high in oxalates, and 90% of them are soluble. Morels, shiitakes, and chanterelles have higher oxalate levels.
Cooking methods can influence the oxalate content of mushrooms. Cooking marginally lowers the soluble oxalate content of mushrooms. Boiling is the most effective method for reducing soluble oxalate content, with a reduction of 30-87%. Steaming is less effective, with a reduction of 5-53%. Baking is only effective for potatoes and does not reduce oxalate in other vegetables. Soaking rice and grains for 12 hours can also lower oxalate content.
The form in which mushrooms are consumed also affects their oxalate content. Fresh mushrooms have varying oxalate levels depending on the type. Drying mushrooms does not change the oxalate content per gram, but it is easy to use more dried mushrooms than fresh, which means consuming more oxalate. Powdered mushrooms have a high oxalate concentration, so it is important to watch portion sizes, especially with powdered and dried mushrooms.
It is important to note that not all oxalate-rich foods will lead to kidney stones. The chemistry is much more complex. However, for those watching their oxalate intake, it is crucial to know the levels in mushrooms and consult a healthcare provider for tailored advice on oxalate-related health issues.
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Wild vs cultivated mushrooms
Mushrooms are a good source of nutrition, but they also contain oxalates, which can cause health issues. While oxalate-related issues are rare, they can be serious, such as acute oxalate nephropathy, a sudden drop in kidney function. Therefore, it is important to manage your oxalate intake, especially if you have a sensitive stomach or are prone to kidney stones.
Wild Mushrooms
Wild mushrooms contain only soluble oxalates, with levels ranging from 29.3 to 40.2 mg per 100 grams of dry mass in their raw state. Cooking these mushrooms can slightly reduce their soluble oxalate content. Wild mushrooms may be exposed to various environmental contaminants, so it is important to cook them to kill harmful microorganisms and bacteria. Wild mushrooms can also be poisonous, so it is crucial to choose edible varieties.
Cultivated Mushrooms
The oxalate content in commercially grown mushrooms ranges from 58.9 to 104.1 mg per 100 grams of dry mass in their raw state. Cooking these mushrooms can affect their oxalate levels, sometimes lowering and sometimes increasing the total oxalate content. Cultivated mushrooms contain mostly insoluble oxalates, except for the ostronskivling and piopino cultivars.
Chaga Mushrooms
Chaga mushrooms, both wild and cultivated, have been associated with oxalate-related health issues, particularly when consumed in high quantities or as supplements. Chaga supplements and powders can deliver a much higher oxalate concentration than whole foods, which can be dangerous for those with kidney issues. However, there is conflicting information about the oxalate levels in Chaga mushrooms, with some studies reporting high or extremely high levels, while others find moderate amounts.
Other Notable Mushrooms
- Oyster Mushrooms: Cultivated oyster mushrooms contain 90% soluble oxalates, making them a moderate risk.
- Morels: Both wild and cultivated morels are rated at a moderate risk for oxalate levels.
- Lion's Mane, Cauliflower Mushroom, and Reishi: These mushrooms are safe for those prone to kidney stones as they do not contain soluble oxalates.
- Shiitake Mushrooms: Shiitake mushrooms are very high in oxalates, but 99% of them are insoluble, so they are not a significant concern.
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Oxalate crystals and toxicity
Oxalate, also known as oxalic acid, is a compound that is naturally produced by the body and can also be found in many food sources, including fruits, vegetables, nuts, grains, and mushrooms. While small amounts of oxalate and calcium are typically present in the urinary tract and do not cause any issues, they can, in some cases, bind together to form calcium oxalate crystals, which may lead to kidney stones.
Calcium oxalate crystals are the most common type of kidney stones, accounting for 80% of cases. These crystals are hard mineral deposits that form in the kidneys and can be extremely painful when passing through the urinary tract. People who are prone to kidney stones may opt to avoid high-oxalate foods, such as spinach, beets, chocolate, tea, nuts, grains, and certain types of mushrooms.
However, it is important to note that not all oxalate-rich foods will lead to kidney stones, as the chemistry is more complex. Additionally, cooking methods can impact the oxalate content of mushrooms, with cooking generally lowering the soluble oxalate content. For example, the oxalate content of raw, commercially grown mushrooms ranged from 58.9 to 104.1 mg/100 g DM, while the values for cooked mushrooms ranged from 48.9 to 124.6 mg/100 g DM.
Furthermore, the type of mushroom and its preparation can affect its oxalate levels. Fresh morels, shiitakes, and chanterelles have higher oxalate levels and should be consumed in moderation. Drying mushrooms does not change their oxalate content per gram, but it may be easier to use more dried mushrooms, leading to a higher oxalate intake. Powdered mushrooms have a more concentrated oxalate content, and consuming them can significantly increase your overall oxalate intake.
In addition to kidney stones, high oxalate levels can lead to a condition called oxalosis, where oxalate builds up in organs and tissues throughout the body, potentially causing damage to bones, blood vessels, the eyes, and even the heart. However, it is worth noting that not everyone with high oxalate intake will experience health issues, as some individuals are better able to eliminate oxalate from their bodies.
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Frequently asked questions
Mushrooms are moderately high in oxalates but have good nutritional value. The oxalate content varies among different types of mushrooms. Oyster mushrooms, for example, are moderately high in oxalates, while Chanterelles, Morels, and Shiitakes have higher oxalate levels.
A sudden increase in oxalate levels in the body can lead to acute oxalate nephropathy, a sudden drop in kidney function caused by the buildup of oxalate crystals in the kidney tubes. Chaga mushroom supplements, in particular, have been linked to cases of oxalate nephropathy due to their high oxalate content.
Cooking mushrooms marginally lowers their soluble oxalate content. Soaking in an acetic acid solution can also significantly reduce the calcium oxalate content.
Other common oxalate-rich foods include spinach, beet greens, chard, chocolate, tea, nuts, grains, and certain supplements.
